Calibration registers can mean different things to different people. For the administrative side of the job, you need to track your calibrated equipment by part number and serial number along with the date last calibrated and the date it is due to be calibrated. For the person doing the calibration of the equipment your register may be something like what value you are measuring, and the plus and minus values allowable. For some equipment this needs to be near the item so the person in the field knows what the 'error' of the item is, i.e. +/- 2%. For the quality assurance people in the 'lab' the same register will tell them wether it passes or fails.
So, does this narrow it down any for you? I don't work on dredging equipment, but you should be able to find a register for your type of equipment from either the manufacturer or Google it.